Anisotropic magnetic properties of a pressure-induced superconductor CeNiGe

CeNiGeの異方的磁性及び磁場誘起超伝導

Thamizhavel, A.*; 中島 弘*; 大開 美子*; 中島 美帆*; 松田 達磨; 芳賀 芳範   ; 杉山 清寛*; 竹内 徹也*; 摂待 力生*; 萩原 政幸*; 金道 浩一*; 大貫 惇睦

Thamizhavel, A.*; Nakashima, Hiroshi*; Obiraki, Yoshiko*; Nakashima, Miho*; Matsuda, Tatsuma; Haga, Yoshinori; Sugiyama, Kiyohiro*; Takeuchi, Tetsuya*; Settai, Rikio*; Hagiwara, Masayuki*; Kindo, Koichi*; Onuki, Yoshichika

フラックス法により、CeNiGeの単結晶育成に成功した。この物質は、圧力によって超伝導状態が誘起される。斜方晶の結晶構造を反映する磁気異方性を持つが、得られた単結晶を用いて、抵抗,比熱,高磁場磁化測定によって詳細な異方性を調べた。二つの反強磁性転移温度を持つことを明らかにし、電子比熱係数も明らかにした。これらの実験をもとに、結晶場のレベルスキームを決めた。

Single crystals of a pressure-induced superconductor CeNiGe have been successfully grown by the flux method. The anisotropic magnetic properties due to the orthorhombic crystal structure have been studied precisely by the electrical resistivity, specific heat, magnetic susceptibility, and high-field magnetization measurements. The results of these measurements confirmed two antiferromagnetic transitions at T=5.0 K and T=4.3 K. The electronic specific heat coefficient obtained from the low-temperature specific heat data amounts to 90 mJ/Kmol Ce. The high-field magnetization for H //[100] shows four magnetic transitions at 11.8, 12.9, 17.5 and 23.9 T with a saturation moment of 0.73 /Ce at 1.3 K. We have also performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and magnetization to understand the magnetocrystalline anisotropy, where the splitting energies of two excited doublets in the CEF scheme are estimated to be 140 and 576 K, respectively.